The present invention relates to an overvarnish unit for applying varnish to a web of printed material and particularly relates to an overvarnish unit for smearing varnish, for example paste varnish, onto a web of printed material in a manner enabling control over the thickness of the varnish deposited on the web and permitting the varnish to be applied to the web in a continuous rather than by a batch type process.
Overvarnishing is the application of a varnish overlay to printed material in the course of a printed process wherein the varnish serves as a protective coating to the printed material. Presently, this is accomplished by means of an ink station forming part of the printing press. That is, the printer will normally dispose a liquid varnish in an ink fountain at an ink station and the varnish will be deposited on the web similarly as if the web was being printed with ink. In conventional printing procedure, the peripheral speed of the printing roller is the same as the linear speed of the web. Thus, contact between the printing roller and the web is made momentarily; i.e., point to point or one line at a time. Stated differently, there is no relative movement between the printing roller and the web as the web passes over the roller. Hence control over the thickness of the varnish applied to the web and its final appearance cannot be maintained.
Further, most varnish coatings applied in conjunction with printing presses utilize a liquid varnish. This liquid varnish is provided in relatively large containers; e.g., five gallon drums. Overvarnishing, however, uses up the varnishing material at a rather rapid rate, particularly in the larger printing roller sizes; e.g., rollers ten, twelve and fourteen inches wide. Consequently, the supply of varnish must be replenished with great frequency; e.g.. every two or three hours. This replenishment, however, requires the machine to be shut down. Accordingly, there has arisen a need for an overvarnish unit which minimizes or eliminates the foregoing and other problems associated with prior overvarnish units and which affords various advantages in construction, operation and end product.